P0340 code....engine wont crank
Thread Starter
Le Mans Master
Joined: Oct 2006
Posts: 5,078
Likes: 19
From: Cumming, GA
Good point. I say this as I had 16k miles on my cam swap with zero issues beating the car to death. Hard shifts, high revs, everything!
Less than 500miles ago I had Yella Terra rockers installed. After the install I heard a rattle noise but all checked out. Now within 500miles I have a TC failure.
I noticed LESS surging after the YT install. I could cruise 70mph in 6th gear with ease up or down a hill and no surging what so ever. With the stock rockers its almost like it was binding the valves and would cause a slight surge when in a high gear rolling down a hill.
Not sure what all this means as it would be speculation if anything, but just thought I might share the history of the cam swap and recent changes.
Thread Starter
Le Mans Master
Joined: Oct 2006
Posts: 5,078
Likes: 19
From: Cumming, GA
After that pop, you should have heard a loud rattling noise as the pistons hit valves. Did you hear that? Whatever you do, do not crank the engine over anymore until you figure out if it is the TC or not. I have spent the last 2 months getting my car back on the road after a TC failure and it is such a crap shoot because no one will give you an exact answer as to the cause or the solution.
Yep it's the TC. Odd thing is NO rattling at all!!!!!!!!! Crazy.
Pulled the heads last night and I feel I am lucky. Not only did it happen less than a mile from my house, but only 3 valves are toast. All other valves are mint, and the pistons just need some minor buffing.
Other than being a PIA and not what I wanted to spend some cash on at the moment, I feel it could have been FAR worst.
Drifting
Joined: Feb 2007
Posts: 1,844
Likes: 12
From: Alpharetta Georgia
You got away much easier than I. I was 210 miles from home when mine broke and almost every cylinder had at least 1 bent valve. Quick comment about your roller rocker install. Many times people run into valvefloat after a roller rocker install because the added mass of the roller rocker overcomes the springs(unless you ran more spring than you needed from the beginning). What kind of valve springs are you running, how many miles on them, and what was your rev limit set to? Had you ripped on the car much after the install?
Thread Starter
Le Mans Master
Joined: Oct 2006
Posts: 5,078
Likes: 19
From: Cumming, GA
You got away much easier than I. I was 210 miles from home when mine broke and almost every cylinder had at least 1 bent valve. Quick comment about your roller rocker install. Many times people run into valvefloat after a roller rocker install because the added mass of the roller rocker overcomes the springs(unless you ran more spring than you needed from the beginning). What kind of valve springs are you running, how many miles on them, and what was your rev limit set to? Had you ripped on the car much after the install?
springs prob have 6-8kmiles on them.
rev limit set to 6800
car sees 6500-6700 everytime out, its a Corvette!:o
Also to speak to what I was referring to before is that rattle noise. Up in the higher rpm after YT install I got this. My best guess is that the YT did me in whether it be what u mentioned above, or something else not sure. With the YT's being the most recent change in the valvetrain I have to believe they affected something leading to the TC failure.
Drifting
Joined: Feb 2007
Posts: 1,844
Likes: 12
From: Alpharetta Georgia
Closely inspect your other valves and pistons(check the other pistons for nicks). You may have been getting some float up high which can lead to some minor PTV contact. This is rough as hell on your TC and your valvetrain. Have you dyno'ed since the YT install and did the car continue to pull hard up high?
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
I had a cam installed 17000 miles ago, I think they reused my factory LS2 chain which had 17000 miles on it. I have an ASP underdrive pulley, stock lifters and rocker arms, Patriot Gold Springs & TI retainers. And I race the heck out of my car.
I am always worried when I see these threads as the common denominator seems to be aftermarket cams and springs. In my friends' case, one was caused by improper clearancing of a double timing set, one was caused by (I believe) using 1.8 ratio rockers with a cam not designed for it (that one kissed the valves twice, broke the chain once), and the third was due to we believe improper installation, as two of the three cam bolts had come out.
These unexplained failures cause me much angst! Even the venerable Glass Slipper investigated and didn't find an exact cause.
Hmm. Maybe my buddy the Clevite Kid can chime in...I think he does this kind of investigation for a living! I'll PM him....
I am always worried when I see these threads as the common denominator seems to be aftermarket cams and springs. In my friends' case, one was caused by improper clearancing of a double timing set, one was caused by (I believe) using 1.8 ratio rockers with a cam not designed for it (that one kissed the valves twice, broke the chain once), and the third was due to we believe improper installation, as two of the three cam bolts had come out.
These unexplained failures cause me much angst! Even the venerable Glass Slipper investigated and didn't find an exact cause.
Hmm. Maybe my buddy the Clevite Kid can chime in...I think he does this kind of investigation for a living! I'll PM him....
Thread Starter
Le Mans Master
Joined: Oct 2006
Posts: 5,078
Likes: 19
From: Cumming, GA
Closely inspect your other valves and pistons(check the other pistons for nicks). You may have been getting some float up high which can lead to some minor PTV contact. This is rough as hell on your TC and your valvetrain. Have you dyno'ed since the YT install and did the car continue to pull hard up high?
I was in a rush and did not have it dynoed after the YT's. Car pulled VERY hard up top on the street.
There is a healthy amount of carbon on all pistons with 27k miles so it was very easy to see which valves hit.
Pretty sure my failure was due to the rocker arm change. Not necessarily a bad install or faulty RA, but simply it threw off the valvetrain geometry. Gonna build the top end stronger this time around for sure.
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Drifting
Joined: Feb 2007
Posts: 1,844
Likes: 12
From: Alpharetta Georgia
I had a cam installed 17000 miles ago, I think they reused my factory LS2 chain which had 17000 miles on it. I have an ASP underdrive pulley, stock lifters and rocker arms, Patriot Gold Springs & TI retainers. And I race the heck out of my car.
I am always worried when I see these threads as the common denominator seems to be aftermarket cams and springs. In my friends' case, one was caused by improper clearancing of a double timing set, one was caused by (I believe) using 1.8 ratio rockers with a cam not designed for it (that one kissed the valves twice, broke the chain once), and the third was due to we believe improper installation, as two of the three cam bolts had come out.
These unexplained failures cause me much angst! Even the venerable Glass Slipper investigated and didn't find an exact cause.
Hmm. Maybe my buddy the Clevite Kid can chime in...I think he does this kind of investigation for a living! I'll PM him....
I am always worried when I see these threads as the common denominator seems to be aftermarket cams and springs. In my friends' case, one was caused by improper clearancing of a double timing set, one was caused by (I believe) using 1.8 ratio rockers with a cam not designed for it (that one kissed the valves twice, broke the chain once), and the third was due to we believe improper installation, as two of the three cam bolts had come out.
These unexplained failures cause me much angst! Even the venerable Glass Slipper investigated and didn't find an exact cause.
Hmm. Maybe my buddy the Clevite Kid can chime in...I think he does this kind of investigation for a living! I'll PM him....
. Makes you rest easy at night right? lol
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
I was in a rush and did not have it dynoed after the YT's. Car pulled VERY hard up top on the street.
There is a healthy amount of carbon on all pistons with 27k miles so it was very easy to see which valves hit.
Pretty sure my failure was due to the rocker arm change. Not necessarily a bad install or faulty RA, but simply it threw off the valvetrain geometry. Gonna build the top end stronger this time around for sure.
There is a healthy amount of carbon on all pistons with 27k miles so it was very easy to see which valves hit.
Pretty sure my failure was due to the rocker arm change. Not necessarily a bad install or faulty RA, but simply it threw off the valvetrain geometry. Gonna build the top end stronger this time around for sure.
Thread Starter
Le Mans Master
Joined: Oct 2006
Posts: 5,078
Likes: 19
From: Cumming, GA
Did you use 1.7 ratio YT's and did you change push rods? The reason I ask is that I'm considering the 1.7 ratio YT's and changing the push rods to stock length Trick Flows. My valve train and cam is stock, I do have a 112 Maggie installed putting out 6 lbs. of boost with the rev limiter set at 6,500 rpm. Any thoughts would be appreciated. The car is an 07 MN 6sp Z51 package with 13,000 trouble free miles on it.
Yes I had the 1.7 YT's installed with the same pushrods used with stock rockers. Not sure the length of those pushrods and wonder if that makes a difference now that you got me thinking.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 264
From: St. Louis, MO
St. Jude Donor '08
BTW here's what my pal The Clevite Kid said:
Originally Posted by The Clevite Kid
From a Failure Analysis perspective, these failures have the hallmarks of fatigue failures, from the accumulation of stress cycles at stresses above the endurance limit of some chain component. Once the microscopic fatigue crack starts, probably just due the the high stresses at extreme RPM, they can then grow during "normal" operation and pop at any time, even under relatively low load.
Therefor a better chain (like the Katech C5-R, I hope) will have a higher endurance limit and a much lower failure probability.
More analysis would take several broken chains and a couple thousand dollars for careful examination in a scanning electron microscope.
Another approach would be to put a Pyrex window in an engine and use a stroboscope aimed at the chain, on an engine dyno, and look for weird harmonic effects.
You can quote any of this in the thread, if you think it would be useful.
Therefor a better chain (like the Katech C5-R, I hope) will have a higher endurance limit and a much lower failure probability.
More analysis would take several broken chains and a couple thousand dollars for careful examination in a scanning electron microscope.
Another approach would be to put a Pyrex window in an engine and use a stroboscope aimed at the chain, on an engine dyno, and look for weird harmonic effects.
You can quote any of this in the thread, if you think it would be useful.
Pro
Joined: Apr 2008
Posts: 525
Likes: 1
From: Vancouver BC
Ha ha ha! Yes indeed!
My engine now has a ticking sound that has been getting steadily worse. I am hoping to tear the engine apart in the near future to see what it is wrong, but my suspicion is that the issue is probably related to the original "incident". I was not able to replace my heads at the time and part of me is wondering if one of the new valves I installed is struggling within a bent valve guide? Hence my recommendation to the OP to have his valve guides inspected.
It has not been possible to definitively say what actually caused my incident but part of me has always wondered if the broken timing chain might have been the "cause" rather than a "result". When the engine came apart I was driving/shifting the car hard. If a timing chain ever was to break on me...it should have probably been at that moment. What piqued my interest was the thread about people who had a Powerbond UD pulley and ended up with a broken timing chain, as I too was/am running an Powerbond UD pulley.
My engine now has a ticking sound that has been getting steadily worse. I am hoping to tear the engine apart in the near future to see what it is wrong, but my suspicion is that the issue is probably related to the original "incident". I was not able to replace my heads at the time and part of me is wondering if one of the new valves I installed is struggling within a bent valve guide? Hence my recommendation to the OP to have his valve guides inspected.
It has not been possible to definitively say what actually caused my incident but part of me has always wondered if the broken timing chain might have been the "cause" rather than a "result". When the engine came apart I was driving/shifting the car hard. If a timing chain ever was to break on me...it should have probably been at that moment. What piqued my interest was the thread about people who had a Powerbond UD pulley and ended up with a broken timing chain, as I too was/am running an Powerbond UD pulley.
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
The stock length is 7.4 inches, being nonajustable milled heads, decked blocks, or increased cam lift could require a shorter push rod. Best to use a pushrod rod length checker to be sure when you deviate from stock valve train geometry. I guess thats why they make pushrods in stock, plus and minus sizes. I don't think it was your rocker arms that caused the problem, if it can be chased down to the rockers being at fault please let us know. When you installed the rockers did you follow the proceedure outlined in the manual? #1 TDC on compresson stroke torque Exh. 1,2,7,8 to 22 ft. lbs and Int.1,3,4,5 then turn the motor 360 degrees #6 TDC on compression torque Exh.3,4,5,6 and Int.2,6,7,8?
Drifting
Joined: Feb 2007
Posts: 1,844
Likes: 12
From: Alpharetta Georgia
^ That method is not mentioned here http://ls1howto.com/index.php?article=1 I just installed all of my rockers, regardless of the positions of the pushrod/lifter on the cam....spun the motor over a couple of times by hand and then re-verified the tq. I haven't had any issue with rockers coming loose. Red locktite on everything though.
BTW, I have an aftermarket cam and my pushrod measurement came to 7.400" with .100 worth of preload. Everyone on LS1tech said running the stock lifters deep helped with valvetrain noise and even a little with power(.080~.100 was the range recommended). I have had no issues with either.
BTW, I have an aftermarket cam and my pushrod measurement came to 7.400" with .100 worth of preload. Everyone on LS1tech said running the stock lifters deep helped with valvetrain noise and even a little with power(.080~.100 was the range recommended). I have had no issues with either.
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
^ That method is not mentioned here http://ls1howto.com/index.php?article=1 I just installed all of my rockers, regardless of the positions of the pushrod/lifter on the cam....spun the motor over a couple of times by hand and then re-verified the tq. I haven't had any issue with rockers coming loose. Red locktite on everything though.
BTW, I have an aftermarket cam and my pushrod measurement came to 7.400" with .100 worth of preload. Everyone on LS1tech said running the stock lifters deep helped with valvetrain noise and even a little with power(.080~.100 was the range recommended). I have had no issues with either.
BTW, I have an aftermarket cam and my pushrod measurement came to 7.400" with .100 worth of preload. Everyone on LS1tech said running the stock lifters deep helped with valvetrain noise and even a little with power(.080~.100 was the range recommended). I have had no issues with either.